Comprehensive 'STEM' (DIY Titration Drop Counter)

Last week, in an effort to keep both my sections of Honors Chemistry moving at the same pace, I found myself with a day to spare in one section. With a unit on lab techniques, specifically titration, quickly approaching, my thought was to pre train this section on the specifics of the laboratory procedure.

Simultaneously, a more playful side of me wanted to bust out the MakeyMakeys from summer science camp and give students some time to explore conductivity, and tinker around a bit repurposing everyday materials to build something just for fun. Then it hit me: Why couldn't we do both?

Back to titration. Digital Drop Counters used to measure the precise volume titrant added to a flask are nearly $100 with the need for more complex software companions for reading data. This it hit me: Could we recreate a Drop Counter using MakeyMakey (along with the pH probes we already have) to simulate the tools we needed for a successful titration? Yes. Sort of! But super fun.

The class devised a simple workflow: first, students wrote a simple program using Scratch that counted clicks when the space bar was pressed. Then they measured the approximate volume of one drop from the burets and added a variable that calculated the volume of liquid added alongside the drop count.

Then for the MakeyMakey! By positioning two wires (one connected to ground and the other to the space button on the MakeyMakey) above the Erlenmyer flask with just enough room for a single drop to complete the circuit, and adding some code to delay the click function for any drops that "stick" to the wires, we were able to accurately measure drops added! Finally something more than a video game controller or banana piano!